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llivrrnn STATES PATENT FFICE.

MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGG SIVITCIIBOARD AND SUPPLY COMPANY, OF SAME PLACE.

MULTIPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent No. 592,417, dated October 26, 1897.

Application filed 11111619, 1893. Serial No. Z78,099. (N0 model.)

To all whom it may concern..-

Be it known that I, MILO G. KELLOGG, of Chicago, in the county of Cook and State of Illinois, haveinvented certain new and useful Improvements in Multiple Switchboards for 'lelephone Exchanges, of which the followin g is a full, clear, concise, and exact description, reference being had to the accompanying drawing, forming a part of this specification.

My invention relates especially to a telephone-exchange system in which the lines are metallic-circuit lines.

My invention consists in a system of calling, answering calls, switching, testing, and clearingout signals which I shall describe and claim in detail.

The accompanying drawing, illustrating my invention, is a diagram of the centraloffice apparatus and connections.

In the drawing two multiple switchboards (marked A A) are shown. As many other switchboards may be used as is necessary for the size and character of the exchange. Each board has a switch or line-terminal for each line of the exchange. The switches are marked 5 .9. Each switch is adapted to receive the loop-switch plugs marked D D and has two contact-pieces g j, with which, respectively, the two contact-pieces m m of the plug form contact when the plug is inserted. Each switch has also two contacts a, b, which are insulated from the rest of the switch parts and are normally (or when a plug is not in the switch) not in contact with each other.

Z l are the switch-holes, into which the switch-plugs D D may be placed for switching the lines together.

c c are the rubber pieces, suitably shaped, on which the metal parts of the switches are respectively mounted.

9 7 maybe called the main-line contacts of the switch, because they are connected with the circuit of the main line, and a b may be called the local contacts of the switch, because they are used in a circuit which is local to the central office of the exchange.

The switch-plugs D D have each two contacts m m. hen a plug is inserted into a switch, its contact-piece m forms connection with the contact-piece g of the switch and its contact-piece m forms connection with the contact-piece j of the switch, while the insulated piece of the plug forces the contactpiece a of the switch into contact with the contact-piece b of the switch, but a and b are not in electric connection with the contactpieces gj of the switch. The switches and the plugs are so shaped and constructed as to produce the switching operations above described. They may, however, be shaped and constructed in other ways, so as to produce substantially the same switching operations.

I11 the construction and arrangement shown there are two contact-pieces of the switch with which the two contact-pieces of the plug respectively form connection when the plug is inserted and two other contact-pieces of the switch which are insulated from said firstmentioned contact-pieces and are normally unconnected with each other, (except through the circuit connections,) but are brought into electrical connection when a plug is inserted into the switch.

Each line has an annunciator (marked 10) and a relay, (marked 00.)

Each relay may be of any suitable construction, with a pair of contact-points which are normally, or when no current is passing through the relaymagnet, closed, but are opened when the magnet is energized by being included in closed circuit with a battery of suitable character. The relay and annunciator of each line may be conveniently mounted in juxtapositionas, for instance,

I on the same frame or support-with the relay in the rear of the annunciator, the drop of the latter being of course at the front of the switchboard.

The two contact-pieces g j of each lineswitch are the main-line contacts of the switch. One side of each metallic-circuit line is connected to one of these contact-pieces, say j, of each switch of the line, and the other side of the line is connected to the other contact pieces of the line, say g. The two sidesof the line are connected together at the central office through the annunciator of the line and the normally closed pair of contacts of the relay of the line.

The line-annunciators are distributed relays.

phone annunciators.

among the various boards and at boards where the calls of the lines are to be answered.

Each operator has as many pairs of plugs D -D as she may need for her work.

The two contact-pieces m m of the plugs are connected together by a flexible conductor and the two contact-pieces m m of the plugs are connected together by another flexible conductor.

Y is a looping-in switch having two levers and threepairs of contact-bolts against which the two levers may alternately be placed in contact. There is one switch Y for each pair of plugs. The two levers are connnected to the two flexible conductors, respectively, of the pair of plugs. The two bolts of one pair are connected together through the operators telephone, (marked 25.) The two bolts of another pair are connected together through the clearing-out annunciator of the pair of plugs. The two bolts of the third pair are connected together through the operators calling-generator.

'v is a clearing-out annunciator, of which there is one of each for each pair of plugs.

B is a test and relay battery, and B is a calling-generator, of which there may be one or more of each for the exchange.

One of the local contacts of each switch, say a, is connected with all ,of the contacts of the same kind, say a, of all the other switches of the exchange. One side of the relay and test battery B is connected to the circuit connection which connects together all of these contact-pieces a a of'the switches of the exchange. One side of each relay is connected to the other side of this relay and test battery B, and the other side of each relay is connected to all the contact-pieces I) Z) of the switches of the line to which the relay belongs;

Each operators telephone should preferably have two coils, and the connection between the two coils is connected by a circuit-wire to the circuit connection which connects the last-mention ed side of the battery B with the A retardation-coil may be placed in this circuit-wire.

For clearness of illustration the main lines and their circuit connections are indicated by solid lines and the local connections of the relay and local contact system of the exchange are represented by broken lines.

One of the local contacts, say b, of each switch is conveniently placed so that one of the contacts of each switch-plug, say m, may be applied to it for testing.

The subscribers-station apparatus may be of the ordinary construction used in telephone exchanges and is in the metallic circuit of the line.

The line-annunciators w 10 may be of the ordinary construction of non-polarized telenunciators o '1; may also be non-polarized and should preferably be of high resistance and retardation to telephone-currents.

The clearing-out an- Each ,operato'rs plug and cord apparatus should be conveniently mounted and arranged for her work.

The operation of the system is as follows: A subscriber on operating his calling-generator to send in a call sends a current through his metallic circuit and through his line-annunciator, which is then in a bridge between the two sides of his metallic-circuit line. The line-annunciator will therefore be operated and will indicate a call. The operator on observing the indication places one of her switch-plugs D into the switch of the line. By so doing she automatically closes the pair of contacts a b of the switch. This brings the relay a: of the line into closed circuit with the battery B, and the relay being thereby energized its contact-points are opened and the bridge between the two sides of the line which contains the line-annunciator is opened and remains open as long as the plug remains in the switch. As soon as the operator places the plug in the switch she places the lovers of the switch Y which belong to the plug in the position where her telephone bridges across between the two contact-pieces of the plug. The operators telephone is therefore in closed circuit with the subscribers metallic-circuit line, and she by conversation finds out what connection the sub scriber wishes. This closed circuit is established by the connection of the two contacts on m of the plug (to which, respectively, the two sides of the operators telephone are connected) with the two contacts 9 and j, respectively, of the switch, which, as stated before, are connected to the two sides of the line. \Vhen the operator finds out what line is wanted, she tests the line wanted, as will hereinafter be indicated, and itshe finds it free or unswitched she places the other plug D of the pair of plugs in the switch of the line wanted. By so doing the contacts a b of that switch are also closed, and the relay of that line, being thereby brought into closed circuit with the battery B, is energized, and

the bridge-circuit of that line through the line-annunciator is also opened by the opening of the pair of contacts of the relay of the line. The operator then moves the levers of the switch Y so that the callinggenerator B is bridged across between the two conductors of the pair of plugs. Calling-current therefore goes in split or derived circuit through The annunciator and operate it. As the line-annunciators are out of circuit with the callinggenerator, when the clearingout signal is sent (the circuit through the annunciators being opened by the pairs of contacts of the line-relays) no current will pass through the line-annunciators. For the same reason no current will pass through the line-annunciators when the operator sends the calling-current to line, as before indicated. The lineannunciator of the two lines will therefore not be operated either when the operator sends a calling-signal or either subscriber sends the clearing-out signal.

W'hen the operator receives the clearing out signal, she removes the plugs from the switches of the two lines. The closed contacts between a and Z) of the two switches are thereby automatically opened and the armatures of the relays of the two lines will take their normal positions, closing the bridges which contain their respective annunciators. The lines are thereby automatically in condition to receive calls from the subscribers.

The test system is as follows: WVhen an operator desires to test any line, she places the contact m of one of her switch-plugs into contact with the contact-piece Z) of the line-switch, the switch Y of the plug having its levers in connection with her telephone. If the line is switched for conversation at any board, a complete circuit is thereby established which contains her telephone and the battery B, and the telephone will respond or click, indicating that the line is switched for use. This complete circuit may be traced as follows: from the contact-piece m of the plug through the cord conductor and switch-lever, through one coil of her telephone, thence through the battery B, thence to the contact a at the switch where the line is switched, thence to contact I) of that switch, and thence to the contact I), to which the contact-piece m is applied for testing. If the line is not switched at any board, no such complete circuit will be established on testing and the telephone will not sound. The operator can therefore determine on testing whether or not a line is switched for use.

When a plug is applied for testing, as above described, and the line tested is switched for conversation, the operators telephone (which is then her test receiving instrument) is shunted by the relay of the line tested. lhis will not, however, divert so much of the battery-current from the telephone that the testsignal will not be audible and distinct.

The drawing and the description heretofore made are for metalliccircuit lines only. The system is, however, adapted to groundcircuit lines or to a mixed system of metallic and ground circuit lines. To adapt it for such a system, the circuits and operation will be exactly as heretofore described, except that the ground-circuit lines are connected to one of the contacts, say 9, of each of their line switches, and the circuit connection which connects the other contacts j j of these switches is connected to ground.

I claim-- 1. In a telephone-exchange system, metallic circuit lines, multiple switchboards, switches, one switch on each board for each line, each switch having two contact-pieces to which respectively the two sides of its line are connected, pairs of loop-switch plugs at each board to connect any two lines into a metallic circuit for conversation each of said loop-plugs being adapted to be in any of said switches at its board and having two contactpieces which when the plug is inserted into any one of said switches form connection with the two contact-pieces of said switches respectively, the two contacts of the two loopplugs of each pair being connected together respectively by two flexible switch-conductors and a clearing-out annunciator with its magnet bridged across between the two sides of said metallic circuit, in combination with a bridge-circuit for each line between its two sides or branches, an annunciator for each line located at a board and with its magnet located in said bridge-circuit of the line between the two sides or branches of the line, and electromagnetic apparatus for each line automatically operated by the switching of the line for conversation to open said bridgecircuit of the line, substantially as set forth.

2. In a telephone-exchange system, metallic-circuit lines, a switchboard, a switch on said board for each line, each switch having two contact-pieces to which respectively the two sides of its line are connected, pairs of loop-switch plugs to connect any two lines into a metallic circuit for conversation by joining the contact-pieces respectively of their switches, each of said loop-plugs being adapted to be in any of said switches at its board and having two contact-pieces which when the plug is inserted into any one of said switches form connection with the two contact-pieces of said switches respectively, the two contacts of the two loop-plugs of each pair being connected together respectively by two flexible switch-conductors and a clearing-out annunciator with its magnet bridged across between the two sides of said metallic circuit, in combination with a bridge-circuit for each line between its two sides or branches, an annunciator for each line with its magnet located in said bridge-circuit of the line between the two sides or branches of the line, and electromagnetic apparatus for each line automatically operated by the switching of the line for conversation to open said bridgecircuit of the line.

3. I11 a telephone-exchange system, telephone-lines, a switchboard, a switch for each line on said board, each switch having two contact-pieces to one of which the direct conductor and to the other of which the return circuit or conductor of the line are connected, pairs of loop-switch plugs to connect anytwo lines into a complete circuit for conversation,

IIS

each of said loop-plugs being adapted to be in any of said switches at its board and having two contact-pieces which when the plug is inserted into any one of said switches form connection with the two contact-pieces of said switches respectively, the two contacts of the two loop-plugs of each pair being connected together respectively by two flexible switchconductors and a clearing-out annunciator with its magnet bridged across between the direct conductor and the return circuit or conductor of said complete circuit, in combination with a bridge or cross-connection circuit for each line between its direct conductor and return circuit or conductor, an annunciator for each line with its magnet located in said bridge-circuit of the line between the two sides or branches of the line, and electromagnetic apparatus for each line automatically operated by the switching of the line for conversation to open said bridge-circuit of the line.

i. In a telephone-exchange system, metallic circuit lines, multiple switchboards,

switches, one switch on each board for each.

line, each switch having two contact-pieces to which respectively the two sides of its line are connected, pairs of loop-switch plugs at each board to connect any two lines into a metallic circuit for conversation by joining the contact-pieces respectively of their switches,

'each of said loop-plugs being adapted to be in any of said switches at its board and having two contact-pieces which when the plug is inserted into any one of said switches form connection with the two contact-pieces of said switches respectively, the two contacts of the two loop-plugs of each pair being connected together respectively by two flexible switchconductors, and a clearing-out annunciator with its magnet bridged across the two sides of said metallic circuit, in combination with a bridge circuit or connection for each line between its two sides or branches, an annunciator for each line located at a switchboard and with its magnet located in said bridgecircuit of its line between the two sides or branches of the line, an electromagnet-relay for each line with a pair of contacts normally, or when the relay-magnet is not energized, closed to each other, said pair of contacts of the relay being also in said bridge-circuit of its line, battery, and means to automatically close the magnet of the relay of aline with battery when and as long as the line is switched for conversation.

In testimony whereof I have hereunto subscribed my name.

MILO G. KELLOGG. Witnesses:

E. S. WALKER, CALVIN DE WOLF. 

